An interesting application of the proposed technology, to which the invention relates preferably, but not exclusively, is the detection of apnea, the monitoring of biological functions such as heart rate and respiration rates, as well as obstructive apnea, particularly for infants.
The invention relates to a system that uses acoustic and electromechanical transducers, such as a piezoelectric film, to measure biological respirative signals over time. Time series analysis techniques are then applied to the measured signals whereby an energy spectrum (periodogram/histogram) is calculated that identifies the rhythmic and pseudo-rhythmic biological functions such as respiration and heart rate and obstructions in the breathing passage (obstructive apnea.).
The apnea monitoring instrument offers researchers, clinicians, parents and other people who are involved in child and adult apnea monitoring an inexpensive way to monitor respiration, heart rate and obstructive apnea without the use of restrictive electrical wiring. It makes available a low cost monitoring instrument to be used as a highly reliable tool for researching and monitoring Sudden Infant Death Syndrome (SIDS).
The apnea monitoring instrument could be used in the home for monitoring infants and adults with breathing problems. It could be used for monitoring fetuses in mothers prior to and while giving birth.
It is a particular objective of the invention to improve the sensitivity, reliability, ease-of-use and usefulness of apnea monitors.
The present invention provides a system whereby passive apnea monitoring can occur. This system uses time series analysis of acoustic and electromechanical signals from the patient to calculate an energy spectrum (periodogram/histogram) thereby displaying spectral-peaks that identify heart and respiration rates, and obstructive apnea. A large piezoelectric film with good frequency response characteristics is used to obtain the acoustic and electromechanical signals from the patient. A microcomputer controlled system (comprising of a CPU with associated peripherals) is used to discriminate signal-to-noise considerations and to determine if an apnea episode is occurring. The patient can lie down on the piezoelectric film, similar to an under mattress sheet, so that even when the patient moves around on the mattress a rendering of the patient""s heart and respiration rates and air passage into the lungs can be monitored.
The instrument monitors the acoustic and electromechanical signals of the patient and calculates an energy spectrum (periodogram/histogram), using time series analysis techniques. The patient lies down on a large piezoelectric film (few microns thick) that has the capability of measuring signals from very high to very low frequencies. The heart and respiration rates as well as obstructive apnea can be observed, detected and measured from the spectral peaks in the resulting energy spectrum. A microcomputing machine provides calculations to determine the energy spectrum and provides for discrimination between noise and a true apnea episode. An alarm calls for assistance in the event of an apnea, including obstructive apnea, or a Sudden Infant Death Syndrome (SIDS) episode.
A preferred apnea monitoring method communicates a patient""s acoustic and electromechanical transmissions to a piezoelectric pad. A voltage signal is produced from the piezoelectric pad, and the voltage signal is transmitted from the piezoelectric pad. The energy spectrum histogram or periodogram is calculated from the transmitted voltage signals, and peaks in the energy spectrum are characterized as heart and respiration rates.
The communicating step comprises communication with pads, in the form of a shirt, sheet or blanket that underlies a patient or a patient""s waterbed.
The transmitting step comprises transmitting via electrical wires or fiber optic cables.
The calculating step comprises calculating versus time signals.
The characterizing step comprises measuring and interpreting visually and via a computer or device that characterizes each of the spectral peaks in the energy spectrum.
Preferably the signal is digitized with an analog-to-digital converter using digital techniques, employing a digitized voltage signal versus a digitized time signal, providing the time series and calculating the energy spectrum using techniques including autocovariance techniques, Fast Fourier Transform techniques, and the zero up-crossing techniques.
Significance of spectral peaks is determined, and an alarm is set off in the event of a problem or potential problem related to respiration or heart functions.
Preferably the patient is placed or lies on the piezoelectric film pad which functions to receive the acoustic and electromechanical signals.
In one form, the piezoelectric pad transmits signals using radio communications or other form of communications that does not require electrical wires or fiber optic cables.
Other biological functions of the living body are monitored using the same pad, processor and time series analysis techniques.
A preferred apnea monitor has a piezoelectric pad for producing a voltage signal from a patient""s acoustic and electromechanical transmissions. A transmitter is connected to the piezoelectric pad for transmitting the voltage signal from the piezoelectric pad. A processor is connected to the transmitter for receiving the voltage signal and calculating the energy spectrum histogram or periodogram from the voltage signal and time signals. A comparator compares peaks in the energy spectrum and characterizes the peaks as heart and respiration rates.
An analog-to-digital converter is connected to the transmitter and to the processor for providing a digitized signal and facilitating using digital techniques in the processor.
A calculator in the processor uses the digitized voltage signal versus digitized time signals, and provides time series used for calculating the energy spectrum using techniques including, but not limited to, autocovariance techniques, Fast Fourier Transform techniques, and the zero up-crossing techniques.
A display measures and interprets visually peaks in the energy spectrum and via the processor for characterizing each of the spectral peaks.
The piezoelectric pad or pads may take the form of a shirt, sheet or blanket that underlies a patient or a patient""s waterbed.
The transmitter comprises electrical wires or fiber optic cables.
An alarm is connected to the processor for determining significance of spectral peaks and setting off the alarm in the event of a problem or potential problem related to respiration or heart functions.
The pad is a piezoelectric film pad and the patient is placed or lies on the piezoelectric film pad which receives the patient""s acoustic and electromechanical signals.
One transmitter is a wireless transmitter whereby the piezoelectric pad transmits signals using radio communications or other form of communications that does not require electrical wires or fiber optic cables.
Other biological functions of the living body are monitored using the same system and time series analysis techniques.
These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings.